The present invention relates to thermostats and other thermal comfort controllers. The present invention particularly relates to thermostats having energy saving estimation capabilities which also use adaptive intelligent temperature recovery.
In traditional thermal comfort control systems, a thermostat initiates heating system operation when the temperature falls below the set point value. The heating system responds by injecting heated air into the enclosure until the temperature within the enclosure has risen to a point above the set point value. In order to achieve more accurate temperature control, typical thermostats use an anticipation element so as to turn off the heating system before the actual set point is achieved. This anticipation causes the actual air temperature for the enclosure to be more accurately controlled at the desired set point. For many situations this type of control results in air temperature that is comfortable for the enclosure""s occupants. The above described principles of traditional thermal comfort control are equally applicable to a cooling system, except that the anticipation function works in reverse, i. e., the anticipator initiates operation of the cooling plant before the set point temperature is exceeded.
With the development of programmable thermostats, occupants are able to modify the temperature within the enclosure at predetermined time periods. Occupants can program the thermostat to follow a temperature set point schedule. For example, thermostats may be programmed to an energy saving condition (setback temperature in heating or setup temperature in cooling) and a comfort condition (setup temperature in heating or setback temperature in cooling). Typically, the thermostat is set to control the temperature at the comfort conditions when the occupants are awake or generally occupy the enclosure. Conversely, the thermostat can control the temperature at energy saving conditions when occupants leave the enclosure and when occupants go to sleep.
The use of setback/setup schedules is known to provide energy savings in many situations. However, conventional programmable thermostats do not provide any information regarding how much energy is actually saved, or how much energy could be saved if the occupant were to modify the temperature set point setup/setback features. Estimates of expected energy savings using the setup/setback features have typically been inferred from tabulated data which is more than 20 years old. The tabulated data was typically based on the generic building constructions from the 1970s which had over-sized HVAC equipment. Because no two building constructions are identical in terms of occupancy, operation, and HVAC equipment sizes and installations, the anticipated energy savings due to setup/setback will be different for each application. The differences are magnified due to various factors such as internal loads, infiltration and exfiltration, solar gains, and the like.
Today, buildings are designed and constructed taking energy conservation measures into consideration. Installed HVAC equipment is much more critically sized to meet the building heating and cooling loads at design conditions, and therefore does not have excess capacity.
Moreover, modern thermostats, such as The Perfect Climate Comfort Controller, Model Nos. PC/W-89xx, and Chronotherm IV, Model Nos. T86xx, manufactured by Honeywell International, Inc., use the tabulated data for energy savings estimates which is based on the assumption that the temperature set point changes from the energy savings value to the comfort value at the programmed time, and not any earlier. Yet, these modern thermostats have incorporated Adaptive Intelligent Recovery (AIR) algorithms. The AIR algorithms provide the thermostat with more efficient heating and cooling system operation that starts the heating/cooling system before the desired time so that the actual temperature meets the desired set point temperature at the specified set point time, rather than the thermostat starting the system at the set point time.
In view of the above, it is apparent that there is a need to provide a climate control system that provides a user with information regarding actual energy consumption for specific enclosures, and accurate estimation of the energy savings for the enclosure if the setup/setback features of a programmable thermostat are modified.
In view of the foregoing, it is an object of the present invention to provide a thermostat that can determine the expected energy savings from temperature set point setup/setback for the building in which the thermostat is used. This thermostat also provides control of an indoor climate to intelligently change temperature according to a predetermined set point setup/setback schedule such that the thermal comfort of the occupants is maintained.
A further object of the invention is to display the expected energy savings information to the enclosure occupant.
In one embodiment of the present invention, the enclosure set point schedule is preprogrammed into the thermostat, including the temperature set points, both at the comfort condition and at the energy saving conditions (setup/setback). This schedule also includes the times of day at which the temperature set points are changed. The system further obtains the outdoor air temperature through the use of an outdoor air temperature sensor. An estimate of the potential energy savings from the programmed setup/setback schedule is then determined for the enclosure. This energy savings is based on the known characteristics of the enclosure and the HVAC equipment in operation. This energy savings information is then presented to the enclosure occupant.
Additionally, the system allows the occupant to modify the temperature schedule, and receive similar information regarding potential energy savings resulting from this modification. For example, an alternative or proposed setup/setback schedule can be input by the occupant. Based on this alternative schedule, the system of the present invention can provide an indication to the user of the amount of energy savings to be expected. The occupant can then determine whether it is desirable to modify the temperature schedule, based upon the estimated energy savings and a desired comfort level.
A further object of the invention is to provide an indication to the user of the amount of energy savings to be expected for a proposed change in single temperature set point operation.
These and other objects not specifically enumerated herein are believed to be addressed by the present invention which contemplates a controller for a climate control system that has an integral energy savings estimator.